multitexturing

Multitexturing is the technique of applying more than one texture to a single geometric primitive during a single rendering pass. In this mode, the graphics hardware samples several textures with separate texture units and combines the results to determine the final color of each pixel.

Historically, multitexturing arose with fixed-function graphics pipelines in the late 1990s. Early GPUs provided a limited number of texture units that could be bound to different textures, and the outputs were combined using texture environment stages or combiner operations. This allowed effects such as multi-layer materials, lightmaps, and decals without requiring multiple rendering passes. As GPUs evolved, the number of texture units increased and programmable shading replaced fixed-function combiners, making multitexturing a standard capability.

Typically, multitexturing involves binding multiple textures (for example, a base color texture, a normal map, and a specular or detail texture) to separate texture units. In fixed-function pipelines, the hardware combines these textures through predefined operations like modulate, add, or blend. In modern programmable pipelines, fragment shaders sample from several textures via sampler uniforms and combine them using shader code, allowing more flexible and complex blending.

Applications include per-pixel lighting with lightmaps, diffuse and detail textures, normal and specular maps, environment or cube maps, and decals or masking textures. Limitations in early hardware included a finite number of texture units and bandwidth constraints; modern GPUs have many units and rely on shader logic to manage complex multitexturing.

Today multitexturing remains a fundamental concept, seamlessly integrated into shaders and widely used for rich, layered material effects.